Following Thursday’s Europa League elimination by arch foes Liverpool, Manchester United’s supporters find themselves in the grip of an unfolding nightmare as Sunday’s derby trip to Manchester City approaches.

The 3-1 aggregate loss to Liverpool left the FA Cup as the only trophy United can win this season and if they lose to local rivals City at the Etihad Stadium, they will be seven points below the Champions League places with only eight games of the season remaining.

Failure to qualify for the Champions League would complete an abject season for United, prompting their under-fire manager Louis van Gaal to admit that the derby is a game that his side simply have to win.

Asked if the match was ‘do-or-die’ in terms of United’s Champions League qualification hopes, Van Gaal replied: “I think so, yes. We are now four points behind, so you have to win.

“Otherwise the gap is bigger and bigger and the matches that you have to play are not so big (many).

“I think then it is seven points and we have to play then eight matches. Then it’s very sharp to recover from that gap.

“It is still possible, but I think it’s difficult then. Because West Ham United is also in front, so it is not only City but West Ham United also.”

Blackening United’s mood yet further is the knowledge that City’s fans are rubbing their hands together in anticipation of a Champions League quarter-final against Paris Saint-Germain after reaching the tournament’s last eight for the first time in their history.

No longer the “noisy neighbours” contemptuously dismissed by former United manager Alex Ferguson, City have emerged as a genuine force in the Sheikh Mansour era and victory for them on Sunday would strengthen the perception that they have usurped United as Manchester’s biggest team.

And yet for all City’s European exploits, they remain a bundle of contradictions in the league, having failed to record back-to-back victories since October, and know that defeat would seriously compromise their own hopes of a top-four finish.

The title seems an even more unlikely objective, with leaders Leicester City 12 points above them, having played a game more, but manager Manuel Pellegrini refuses to accept that his side’s challenge is over.

“In football when you have a mathematical chance, you cannot think you cannot do it,” said the Chilean, whose side are seeking a third consecutive home win over United.

“It’s a winning mentality: win the next game and then see which team has the most points.

“I think that a derby is always dangerous, regardless of the position of both teams. If it’s in the Premier League it’s doubly dangerous.

“It’s hard because they have good players. United have a very good squad. It doesn’t matter which (players) play or in which way they play; they’re always a dangerous team.

“It’s a target (to finish above United), but it’s not the most important thing. The most important thing is to finish first, then you’re above all other teams.”

City captain Vincent Kompany has been ruled out after suffering yet another calf injury — his 14th in eight years — in Tuesday’s 0-0 draw with Dynamo Kiev, while fellow centre-back Nicolas Otamendi faces a fitness test after being forced off in the same game with a dead leg.

Midfield trio Kevin De Bruyne, Samir Nasri and Fabian Delph will also be absent, although Pellegrini revealed that they are due to return to action with the club’s under-21s during the international break.

United have injury problems of their own, with midfielder Ander Herrera a doubt due to a groin injury and captain Wayne Rooney, left-back Luke Shaw and defender Phil Jones all still sidelined.

But winger-turned-right-back Antonio Valencia is in contention after making his first appearance after five months out with a broken foot as a half-time substitute against Liverpool.

Ashley Young and Cameron Borthwick-Jackson could also feature after returning to training following injury.